1. Field of the Invention
The invention relates to an image pickup apparatus suitable for nighttime picture taking and an image pickup method for the apparatus.
2. Description of the Related Art
A known image pickup apparatus is described in, for example, Japanese Patent Application Laid-Open Publication No. HEI 5-56341, in which incident light via an image pickup optical system is subjected to photoelectric conversion by a CCD, and is then output. This image pickup apparatus controls the amount of light transmitted to an image pickup optical system and the light accumulation time of image pickup elements, and variably controls the gain of output of the image pickup elements. During a predetermined picture taking mode, the apparatus performs such a control as to increase the gain, in order to reduce the set time of light accumulation. Thus, the apparatus attempts to optimize exposure control regardless of picture taking conditions.
However, this type of image pickup apparatus still suffers from problems of, for example, halation in picked-up images depending on picture taking environments. For example, if such an image pickup apparatus is used as a visual recognition support system that assists a driver of a vehicle in visual recognition during a nighttime run of the vehicle, the image pickup output is set high for visually recognition of a pedestrian or the like ahead in the running direction of the vehicle in a dark condition. However, with such a setting, the effect of halation becomes great, for example, when the image pickup apparatus is illuminated by the headlights of an oncoming vehicle. In such a case, therefore, the image pickup apparatus cannot appropriately take pictures.